To insert an item at a specific index in an array is by using the splice() method. This method allows you to add, remove, and replace elements in an array.
Here's an example of how you can use the splice() method to insert an item at a specific index:
const array = [1, 2, 3, 4];
const index = 2;
const newItem = 5;
array.splice(index, 0, newItem);
console.log(array); // Output: [1, 2, 5, 3, 4]
In the example above, we have an array with four elements. We want to insert a new item with the value of 5 at index 2 (which is the third position in the array, since arrays are zero-indexed).
To do this, we call the splice() method on the array and pass three arguments:
The index at which to start changing the array (in this case, index).
The number of elements to remove (in this case, 0).
The new element to insert (in this case, newItem).
The splice() method then modifies the original array by adding the new item at the specified index and shifting all the other elements to the right .